The present invention relates generally to fluid refill valves for fluid-actuated pumps and, more particularly, to such a fluid refill valve which is fluid flow limiting.
There are many varieties of commercially available fluid-actuated pumping systems. In many such pumping systems, it is necessary to maintain the amount of actuating fluid in a fluid chamber portion of the pumping system within predetermined fluid limits for proper operation of the pumping system. Accordingly, many such pumping systems include a fluid refill valve in communication with both the fluid chamber and a source of activating or operating fluid. When the fluid within the fluid chamber falls below a predetermined level necessary for proper operation of the pumping system, the fluid refill valve is opened during at least a portion of the pumping cycle to permit replacement or make-up fluid to flow from the fluid source, through the fluid refill valve and into the fluid chamber. The fluid refill valve continues to open during the corresponding portion of subsequent pumping cycles until the level of fluid within the fluid chamber has increased above the predetermined level to provide sufficient fluid for proper operation of the pumping system.
Fluid refill valves of the type described above are generally opened based upon the suction pressure in the fluid chamber of the pump during the suction portion of the pumping cycle. When the fluid within the fluid chamber falls below the predetermined level, further operation of the pump results in the creation of an increased suction pressure (becoming more negative with respect to atmospheric pressure) within the fluid chamber during the suction portion of the cycle. The increased suction pressure causes the fluid refill valve to open to permit the flow of small amounts of make-up fluid to the fluid chamber with each suction stroke of the pump. As the make-up fluid is added to the fluid chamber, the suction pressure within the fluid chamber diminishes and, eventually, the suction pressure decreases below the pressure necessary to open the refill valve and the valve remains closed, preventing the further flow of make-up fluid to the fluid chamber.
While fluid refill valves of the type described above are generally effective in maintaining the proper level of fluid within the fluid chamber during normal pumping system operation, during certain abnormal pumping system conditions, fluid refill valves of this type can cause the fluid chamber to become overfilled, possibly resulting in a deterioration and/or failure of one or more components of the pumping system. For example, if the suction pressure within the valve chamber is increased due to a non-fluid level reason, such as a mistakenly closed suction line valve, a restriction in a suction line or any other similar abnormality, the suction pressure within the fluid chamber will increase, causing the fluid refill valve to be in the open position each time the pump is in the pertinent portion of the pumping cycle, permitting excessive amounts of make-up fluid to flow into the fluid chamber, whether or not such make-up fluid is needed. Since under such circumstances the filling of the fluid chamber does not decrease the suction pressure in the fluid chamber, the refill valve will remain in the open condition during the corresponding portion of each pumping cycle. Eventually, the fluid chamber will become overfilled, preventing the proper operation of the pump and possibly causing a deterioration or serious malfunction within the pumping system.
The present invention overcomes the potential overfill problems associated with such a fluid refill valve by providing means for limiting the flow of fluid through the oil refill valve, particularly when the fluid refill valve is opened due to an abnormally high suction pressure within the fluid chamber.